1. Field of the Invention
The present invention relates to a power divider and a dual-output radio transmitter, and more particularly, to a power divider and dual-output radio transmitter has small volume and simple structure, and is suitable for multi-band or wideband operations.
2. Description of the Prior Art
With the advancement of wireless communication, wireless communication systems supporting multi-input and multi-output (MIMO) technology, such as IEEE 802.11 compatible systems, are increasing in number, in order to improve transmission efficiency and rate, as well as quality of services. The concept of MIMO is to transmit and receive radio signals via multiple (or multi-set of) antennas, such that system throughput and transmitting range can be increased without additional bandwidth or transmit power expenditure, and thus, spectrum efficiency and transmitting rate can be enhanced.
To transmit and receive signals via smart antennas in a MIMO system, a corresponding radio-frequency (RF) processing circuit is required to properly distribute transmitting signals to each antenna. Therefore, a power divider is necessary. For example, in a 2T/2R (2 transmitters, 2 receivers) MIMO system, an RF signal processing circuit may divide a signal into two RF signals with the same power and 90-degree phase difference, so as to emit the two RF signals via two transmission antennas. The power divider capable of reaching 90-degree phase difference is an important component in the field of RF signal processing. However, the prior art power divider of 90-degree phase difference requires large layout area. Besides that, the prior art power divider is usually designed for narrow band or single band applications, leading to increase of power consumption and deviation of phase difference when the power divider is used in wideband or multi-band operations.